1. Field of the Invention
This invention relates to a system and method for producing an intensity test signal for a medical monochrome video monitor.
2. Description of the Related Art
High performance monochrome video monitors are typically used in the field of medical diagnostic video imaging. This use requires a high quality video output from the monitor. However, the video quality of a monitor does degrade with time. Therefore, it is important for the calibre of the monitor output to be checked regularly. Medical monitors are typically tested by trained technicians with the aid of devices which cause the monitors to display test patterns for the technician to view for defocussing and distortions. Generally the technicians also visually check the intensity of the monitor's output in response to these test patterns. Visual intensity testing is, however, only an approximate measure of the intensity response of the monitor, not only because of its subjective element from technician to technician, but also because of the impact of variable ambient light conditions. Further, medical monochrome monitors generally operate with one of two line rates: 525 lines per screen or 1049 lines per screen. This requires different test equipment for monitors with different line rates.
When a medical monitor is in use, an operator who is not satisfied with a particular image may adjust the brightness and contrast controls of the monitor in an attempt to improve the image clarity. However, this could wash out grey-scale gradations in the image thereby obscuring potentially important image features. Further, these reset controls will impact on future use of the monitor and, when such a reset monitor comes up for testing, it is not certain that the technician will properly return the brightness and contrast controls to their optimal settings.
This invention seeks to overcome drawbacks of the known prior art.